Surveys on the approval of Putin and the invasion of Ukraine in 2014 showed numbers between 80% - 90% of people approving the war.

I assume - one would need to check - that the majority of people who left Russia after 2022 did not support the war, so those left should be on the lower end.

"20% of Russians were ready to vote for an anti-war party in the last elections"

Yes, as I've said, approval dropped when Ukraine hit oil infra and gas prices went up, I can see 20% as a number. Nevertheless as show by approval ratings after 2014, that number was lower until people got hit by the impact of the war themselves.